Abstract
In ASDEX Upgrade, the propagation of cold pulses induced by type-I edge localized modes (ELMs) is studied using electron cyclotron emission measurements, in a dataset of plasmas with moderate triangularity. It is found that the edge safety factor or the plasma current are the main determining parameters for the inward penetration of the Te perturbations. With increasing plasma current the ELM penetration is more shallow in spite of the stronger ELMs. Estimates of the heat pulse diffusivity show that the corresponding transport is too large to be representative of the inter-ELM phase. Ergodization of the plasma edge during ELMs is a possible explanation for the observed properties of the cold pulse propagation, which is qualitatively consistent with non-linear magneto-hydro-dynamic simulations.
Highlights
Understanding the electron heat transport in tokamaks is necessary to predict the performance of future fusion reactors
In ASDEX Upgrade, the propagation of cold pulses induced by type-I edge localized modes (ELMs) is studied using electron cyclotron emission measurements, in a dataset of plasmas with moderate triangularity
Ergodization of the plasma edge during ELMs is a possible explanation for the observed properties of the cold pulse propagation, which is qualitatively consistent with non-linear magneto-hydro-dynamic simulations
Summary
Understanding the electron heat transport in tokamaks is necessary to predict the performance of future fusion reactors While it has been widely studied in the core [1, 2], less attention has been given to its characterization in the edge-core coupling region, say 0.7 ρpol 0.95 (where ρpol is the normalized poloidal radius). The article is organized as follows: in section 2, the database of ASDEX Upgrade plasmas used in this study is described; a quantification of the inward penetration of an ELM-induced Te perturbation is defined.
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